The lead acid battery can be considered the earliest type of rechargeable battery, and lead acid chemistry remains the most commonly used battery chemistry. The active materials in a lead acid battery generally include lead dioxide (PbO2), lead (Pb), and sulfuric acid (H2SO4) which also acts as the electrolyte. To assemble a lead acid battery, PbO2 and Pb active materials can be pasted and cured onto monopolar lead current collectors to form positive and negative plates, from which an electrochemical cell can be formed with H2SO4 electrolyte. The cells are generally arranged electrically in a parallel configuration such that the voltage of the battery is proportional to the number of cells in the battery pack.